8 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.21 



(1861). The fact that it is based not on one character, but on multiple 

 characters, each the manifestation of a sound developmental principle, 

 argues well for its widespread use. In brief, Balss recognizes four cri- 

 teria of development which may be looked for in each of the Alcockian 

 subfamilies: (1) the presence of the interantennular spine, which is 

 the true rostrum of the zoea, the so-called rostrum of the adult being a 

 secondary outgrowth of the front {fide Cano) ; (2) the degree of fusion 

 of the paired rostral horns along the median line to form a single beak 

 or rostrum; (3) the amount of coalescence of the abdominal segments 

 in the two sexes; and (4) the presence or absence of a supplementary 

 spine ("Interkalardorn") between the pre- and postorbital spines. The 

 most primitive genera in each group would then be characterized by 

 having an interantennular spine, a double rostrum, seven free abdominal 

 segments in both sexes, and a spine intercalated between the inner and 

 outer orbital spines. (This is true of Macrocheira of the Inachinae, of 

 Notolopas of the Pisinae, and of Maiopsis of the Majinae. It is not true 

 of any genus of the Acanthonychinae, all of which lack the intercalated 

 spine.) 



The nature and extent of dislocation of the present (Rathbun) 

 arrangement caused by the application of this system to the New World 

 forms is best illustrated by the Inachinae, where Eurypodius is lifted 

 from its time-honored position next Oregonia and placed beside Macro- 

 cheira, the most primitive member of the group. At the same time the 

 order of the remaining genera is reversed, the subfamily attaining its 

 highest development with long-limbed, long-beaked forms like Podochela 

 and Stenorynchus, rather than with short-horned, doubly-rostrate Col- 

 lodes, with which the present arrangement ends. 



In extending the system of classification proposed by Balss and in 

 adapting it for the first time to the American brachyuran fauna, the writer 

 has seen fit to retain for practical reasons the subfamilial designations of 

 Alcock, with the exception of the Ophthalmiinae, withdrawn by Balss 

 from the Majinae, where it constituted the subsection Stenocionopoida 

 of Alcock, and the restricted subfamily Majinae, called by Alcock the 

 Maioida. This is done to take advantage of Stephensen's (1945) analysis 

 by subfamilies of the male pleopods, and because of belief that the 

 presence or absence of a single spine, even though it be the intercalated 

 orbital spine, does not in itself constitute sufficient grounds for the setting 

 up of new subfamilies. Rather, this would appear to be inherent in the 

 process of evolution of the orbit, which, according to Balss, is proceeding 

 independently, but along parallel lines, in each of the Alcockian sub- 



